Thread guide for sewing machines

ABSTRACT

A THREAD GUIDE FOR DIRECTING THREAD TO THE TAKE-UP OF A SEWING MACHINE WITH A NEEDLE BAR INTERRUPTING MECHANISM FOR ENABLING THE SEWING MACHINE TO SKIP STITCHES. THE THREAD GUIDE IS CONSTRUCTED AND ARRANGED WITH THREAD RETAINING MEANS TO PREVENT THE SURPLUS THREAD OCCASIONED BY OPERATION OF THE SKIP-STITCH MECHANISM FROM DISENGAGING THE THREAD GUIDE OR FROM BECOMING SNARLED OR ENTANGLED THEREWITH.

Sept. 20, 1971 sun ILLES ETAL THREAD GUIDE FOR SEWING MACHINES Filed July 16, 1970 s fi (n m0 0 80 mm N .A I e r mm .00 W .WO 88 V. B

WITNESS 5 6 00 fla g WWW United States Patent 3,605,659 THREAD GUIDE FOR SEWING MACHINES Stephen J. Illes, Summit, N.J., and Salvatore A. DOrro, Staten Island, N.Y., assignors to The Singer Company, New York, N.Y.

Filed July 16, 1970, Ser. No. 55,329 Int. Cl. D051 1/00, 3/02, 49/00 US. Cl. 112-154 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION In sewing machines equipped with skip-stitch mechanism particularly of the type in which the needle bar reciprocation is interrupted in order to prevent stitch formation, a problem can arise because of the presence of abnormal amounts of slack thread in the needle thread regulating system of the sewing machine.

The copending US. patent application Ser. No. 848,- 175, filed Aug. 7, 1969 of E. J. Tullman, now Pat. No. 3,559,607 to which reference may be had, discloses a skipstitch mechanism of the type referred to above in which needle bar reciprocation is interrupted in order to effect skip stitching. When the needle bar reciprocation is interrupted and the remaining mechanism of the sewing machine including the needle thread take-up mechanism continue to operate, the needle thread which in sewing is taken down through the work by the needle and seized and manipulated by the loop taker, is during skip-stitch operation formed into an abnormally large slack thread loop adjacent to the takeup member. With conventional thread guides, it is possible for such abnormal slack needle thread to become entangled, to form uncontrolled loops which may lasso or snag the thread guides with resulting thread breakage, or to fall, slip or become concatenated so as to become disengaged from the thread guides thus to render the needle thread regulating system inoperative.

BRIEF SUMMARY OF THE INVENTION It is an object of this invention to provide a thread guide suitable for directing needle thread to a take-up member of a sewing machine having a skip-stitch mechanism in which the thread guide is provided with a thread retainer for accommodating the abnormal slack thread incident to skip-stitching and preventing unthreading of the thread guide or snagging of the slack thread thereon.

The above objects are attained by providing a thread guiding stud with a thread retaining blade having an inturned thread trapping tab which is spaced from the thread guiding stud a distance at least equal to half the length of the surplus needle thread occasioned in the system during skip stitching with the tab arranged to project into a shallow cavity in the sewing machine so as to prevent disengagement of the thread from the thread guide.

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With the above and additional objects and advantages in view as will hereinafter appear, this invention comprises the devices, combinations and arrangements of parts hereinafter described and illustrated in the accompanying drawings of a preferred embodiment in which:

FIG. 1 is a side elevational view of a portion of a sewing machine with part of the machine frame broken away to illustrate the separable needle bar drive of a skipstitch mechanism and having the thread guide of this invention applied thereto,

FIG. 2 is a cross-sectional view taken substantially along line 2-2 of FIG. 1, and

FIG. 3 is an enlarged perspective view of the thread guide of this invention.

In FIG. 1 a portion of a sewing machine is illustrated including a bracket arm 11 of a sewing machine frame which overhangs a work supporting bed 12. Carried for endwise reciprocation in the bracket arm is a needle bar 13 to which a thread carrying eye-pointed needle 14 may be secured by a needle clamp 15. Reciprocation of the needle results in penetration of the work fabric on a throat plate 16 on the bed which supports the work fabric against the thrust of the needle and on which a work fabric is held by a presser foot 17 carried by a presser bar 18 in the bracket arm. A main shaft 20 journaled in the bracket arm carries a counterbalanced crank 21 which imparts endwise reciprocation to the needle bar by Way of a drive link 22 which embraces a lateral stud projecting from the needle bar. Also oscillated by the counterbalanced crank 21 is a needle thread take-up arm 24 which partakes of a path of oscillation in a plane substantially parallel to the path of needle bar reciprocation.

The needle bar 13 at the upper extremity is journaled in a gate 26 shiftably supported in the bracket arm for imparting lateral jogging movement to the needle for the production of zigzag stitches. In FIG. 1, mechanism on the needle bar and indicated generally by the reference character 30 is provided for interrupting endwise reciprocatory movement of the need-1e bar during operation of the sewing machine. Also illustrated in FIG. 1 is a stationary bracket 31 which serves to contact the mechanism 30 on the needle bar to affect interruption of needle reciprocation under certain conditions of machine operation, and a stationary bracket 32 which serves also to maintain the interrupted needle bar in elevated position and to prevent improper operation of the needle bar interruption mechanism. The above mentioned parts 30, 31 and 32 are associated with a skip-stitch mechanism and may be constructed as described in greater detail in the above referenced US. patent application Ser. No. 848,175 to which reference has been made. It will be understood that when the needle bar reciprocation is interrupted, the needle bar will remain in an elevated position while the remainder of the actuating mechanism of the sewing machine continues to operate, thereby resulting in a secession or skip ping of stitches during needle bar interruption.

As shown in FIG. 1, the end of the sewing machine bracket arm 11 may be closed by an end cover plate 40 to conceal the needle bar and skip-stitch mechanism, and the top of the bracket arm 11 may be closed by a top cover plate 41. The top cover plate may be formed with a slot 42 accommodating the take-up arm 24 at the top of its stroke and adjacent the slot 42 the top cover plate carries a thread tension device 43 which includes a check spring 44. The thread tensioning device may be constructed in accordance with the copending US. patent application Ser. No. 75,430, filed Sept. 25, 1970 to which reference may be had for a more detailed description thereof. The needle thread T is directed from a source of supply (not shown) to the thread tensioning device 43 and the check spring 44, then vertically downwardly to the thread guide 50 of this invention, then to the take-up arm 24 and downwardly to a thread guide 51 beneath the bracket arm, a thread guide 52 on the needle clamp and to the needle 14.

The thread guide 50 of this invention of which the details are illustrated in FIGS. 2 and 3 comprises a cylindrical thread engaging stud 60 formed with a smooth cylindrical extremity 61 and with a striated extremity 62 which, as illustrated in FIG. 2, is adapted to be forced into a bore 63 formed in the front face of the sewing machine bracket arm 11. Preferably, the stud 60 is forced sufficiently far into the bore 63 so that only the smooth extremity 61 of the stud projects exteriorly of the machine frame for engagement with the thread, and an interference fit of the striated extremity 62 of the stud in the bore 63 is preferably so as to maintain the thread guide in selected position on the sewing machine during assembly. A set screw 64 threaded in the sewing machine bracket arm and intersecting the bore 63 is used as a final assembly step in locking the thread guide in position on the sewing machine.

A fiat rigid blade 70 is secured to the smooth extremity 61 of the stud 60 and extends substantially perpendicularly to the stud 60. The free extremity of the plate 70 is formed with a pair of laterally extending tabs 71 and 72, one at each side of the plate 70. Since the tabs 71 and 72 are identical other than being of the opposite hand, like reference characters will be used to designate the parts thereof. Each of the tabs 71 and 72 are inturned along the juncture 73 with the plate 70 to extend from the plate substantially parallel to the stud 60 and on the same side of the blade from which the stud extends. Preferably, each of the tabs 71 and 72 are equidistant from the stud 60 and formed with a top edge 75 which extends perpendicularly to the plate 70. Each of the tabs 71 and 72 is formed with a bottom edge 77 inclined as shown best in FIGS. 2 and 3 outwardly from the plate and upwardly toward the stud 60.

As illustrated in FIGS. 1 and 2 the bracket arm 11 beneath the bore 63 is formed with a shallow recess or cavity 80 and the thread guide 50 is secured in the bracket arm so as to position the free extremity of the tabs 71 and 72 into the shallow recess 80. The tabs 71 and 72 are preferably positioned in that space relation to the bottom of the recess 80 as to readily admit a needle thread T to be passed therebetween; and because of the inclined bottom edges 77 of the tabs, the thread may be readily introduced into the space between the plate 70' and the bracket arm 11 while the perpendicular top edges 75 of the tabs deter accidental escape of the thread from the space between the plate 70 and the bracket arm 11 of the machine.

Preferably, the thread guide 50 is arranged as shown in FIG. 1 with the plate 70 extending from the stud in a direction diametrically opposite the thread tensioning device 43. In this way, when the needle bar reciprocation is interrupted and an abnormal amount of slack thread is occasioned in the needle thread regulating system from the thread tensioning device 43 to the needle 14, the thread guide 50 will be positioned best to deter tangling or catching of this abnormal slack thread thereon. The tabs 71 and 72 are preferably spaced from the stud 60 at least a distance equal to one-half of the surplus length of thread which exists in the needle thread controlling system during skip stitching so that even if all of the surplus thread becomes concentrated at the thread guide 50', no opportunity for escape of the thread from the thread guide will be presented. The blade 74) thus provides a thread retaining means for preventing the thread from lassoing any portion of the thread guide 50. The arrangement of the tabs 71 and 72 projecting into the cavity 84} permits the thread to be introduced readily to the thread guide and effectively prevents accidental escape of the thread therefrom during machine operation. The present invention therefore provides a simple and eflfective means for coping with the large amounts of abnormal slack thread which occur when a skip-stitch mechanism is employed on a sewing machine.

Having thus set forth the nature of this invention, "what is claimed herein is:

1. In a sewing machine having an endwise reciprocatory needle and a needle thread regulating system including a needle thread take-up member, in combination a skip-stitch mechanism eifective during operation of said sewing machine for interrupting endwise reciprocation of said needle, said needle thread take-up member developing a length of surplus needle thread in said needle thread regulating system upon operation of said slip stitch mechanism, and a thread guide for directing thread to said take-up member, said thread guide comprising a thread guiding stud projecting from said sewing machine, a thread retaining blade secured to the free extremity of said stud, an inturned tab formed on said blade at a distance from said stud which is equal to at least one-half the length of surplus needle thread which is developed in said needle thread regulating system upon operation of said skip-stitch mechanism, said sewing machine being formed with a tab accommodating cavity and means for securing said thread guiding stud in said sewing machine with said tab projecting into said cavity.

2. The combination as set forth in claim 1 in which that side of said inturned tab which faces toward said thread guiding stud extends substantially perpendicularly from said thread retaining blade to deter egress of thread from between sewing machine and said thread retaining blade, and in which that side of said inturned tab which faces away from said thread guiding stud is inclined away from said thread retaining blade and toward said thread guiding stud to facilitate insertion of thread between said sewing machine an said thread retaining blade.

3. The combination as set forth in claim 2 in which substantially identical inturned tabs are provided at each side of said thread retaining blade, each of said tabs being spaced equidistant from said thread guiding stud.

4. The combination as set forth in claim 1 in which a thread tensioning device is carried on said sewing machine from which thread extends to said thread guide for directing the thread to said take-up member, and in which said thread guide is secured in said sewing machine with the tab on said thread retaining blade disposed on the diametrically opposite side of said stud from said thread tensioning device.

5. In a sewing machine having a frame including a Work supporting bed, a bracket arm overhanging said bed, and a top cover closing said bracket arm, an endwise reciprocatory needle carried substantially vertically in said bracket arm, and a needle thread regulating system including a thread tensioning device carried on said bracket arm top cover and a take-up arm oscillatable substantially vertically in said bracket arm, in combination a skip-stitch mechanism effective during operation of said sewing machine for interrupting endwise reciprocation of said needle, said take-up arm developing a length of surplus needle thread in said needle thread regulating system upon operation of said skip-stitch mechanism, and a thread guide for directing thread from said thread tensioning device to said take-up arm, said thread guide comprising a thread guiding stud secured in said bracket arm beneath said thread tensioning device, a thread retaining blade secured to the free extremity of said stud, an inturned tab formed on said blade at a distance from said stud which is equal to at least one-half of the length of surplus thread which is developed in said needle thread regulating system upon operation of said skip-stitch mechanism, said bracket arm being formed with a shallow cavity vertically beneath said thread guiding stud, and means for securing said thread guiding stud in said bracket arm with said tab projecting into said cavity.

6. A thread guide for use exteriorly on a sewing machine frame and comprising a thread guiding stud having a plain cylindrical thread engaging extremity and an adjoining extremity formed with raised striations and adapted to be forced into a thread guide accommodating aperture in a sewing machine frame, a flat elongate blade secured to the thread engaging extremity of said thread guiding stud, and a pair of similarly shaped tabs formed laterally one at each side of said blade equidistant from said stud, said tabs each being bent at the juncture with said blade so as to extend substantially parallel with said Stud.

References Cited UNITED STATES PATENTS JORDAN FRANKLIN, Primary Examiner G. H. KRIZMANICH, Assistant Examiner US. Cl. X.R. 

